Cytotoxic T-lymphocytes (CTLs) are believed to be the major host defense mechanism in response to a variety of viral infections and neoplastic or cancerous growth. These cells eliminate infected or transformed cells by recognizing antigen fragments in association with various molecules (termed class I MHC molecules) on the infected or transformed cells. CTLs may be induced experimentally by cytoplasmic loading of certain soluble antigens within specific cells. Immunization with the soluble antigen alone is generally insufficient for specific cytotoxic T-lymphocyte induction.
One method by which CTL response may be induced involves the use of recombinant engineering techniques to incorporate critical components of an antigen in question into the genome of a benign infectious agent. The aim of such a strategy is to generate antigen-specific cytotoxic T-lymphocyte responses to the desired epitope by subjecting the host to a mild, self-limiting infection. Chimeric vectors have been described using vaccinia, polio, adeno- and retro-viruses, as well as bacteria such as Listeria and BCG. For example, Takahashi et al. 85 Proc. Natl. Acad. Sci., USA 3105, 1988 describe use of recombinant vaccinia virus expressing the HIV gpl60 envelope gene as a potential tool for induction of cytotoxic T-lymphocytes.
A second method by which a cell mediated response may be induced involves the use of adjuvants. While the art appears replete with discussion of the use of adjuvants, it is unclear in such art whether cell mediated immunity was induced and whether such cell mediated immunity included a cytotoxic T-lymphocyte response. The following, however, are representative of various publications in this area.
Stover et al., 351 Nature 456, 1991 (not admitted to be prior art to the present application) describes a CTL response to .beta.-galactosidase using recombinant BCG containing a .beta.-galactosidase gene. No such response was detected using incomplete Freund's adjuvant and .beta.-galactosidase.
Mitchell et al., 8 J. Clinical Oncology 856, 1990 (which is not admitted to be prior art to the present invention) describe treatment of metatastic melanoma patients with an adjuvant termed "DETOX" and allogeneic melanoma lysates administered five times over a period of six weeks. In a small portion of the patients an increase in cytolytic T-cells was observed. The authors describe a need to enhance the level of cytotoxic T-lymphocyte production, and suggest a combined therapy of adjuvant with Interleukin-2, as well as a pretreatment with cyclophosphamide to diminish the level of tumor specific T-suppressor cells that might exist. DETOX includes detoxified endotoxin (monophosphoryl lipid A) from Salmonella minnesota, cell wall skeletons of Mycobacterium phlei, squalene oil and emulsifier.
Allison and Gregoriadis, 11 Immunology Today 427, 1990 (which is not admitted to be prior art to the present invention) note that the only adjuvant "autho-present invention) note that the only adjuvant "authorized for use" in human vaccines is aluminum salts (alum) which does not consistently elicit cell mediated immunity. Allison and Gregoriadis state "[t]here is, therefore, a need to develop adjuvants with the efficacy of Freund's complete adjuvant but without its various side effects such as granulomas."They go on to state that three possible strategies exist, for example, the use of liposomes; the use of adjuvants, termed immuno-stimulating complexes (ISCOMs, which include saponin or Quil A (a triterpenoid with two carbohydrate chains), cholesterol, and phosphatidyl choline) which are authorized for use in an influenza vaccine for horses (Morein et al., Immunological Adjuvants and Vaccines, Plenum Press, 153); and the use of an emulsion (SAF) of squalene or Squalane (with or without a pluronic agent) and muramyl dipeptide (MDP). SAF is said to elicit a cell mediated immunity in mice, although it "has long been thought that subunit antigens cannot elicit cytotoxic T-cell (CTL) responses."
Takahashi et al., 344 Nature 873, 1990, describe class II restricted helper and cytotoxic T-lymphocyte induction by use of ISCOMs with a single subcutaneous immunization in mice. They state that Freund's adjuvant, incomplete Freund's adjuvant, and phosphate buffered saline did not induce cytotoxic T-lymphocyte activity against the targets in which they were interested. They state that, in contrast to results with other forms of exogenous soluble protein antigen, they have shown that it is possible to prime antigen specific MHC class I restricted CD8.sup.+ CD4.sup.- CTL by immunization with exogenous intact protein using ISCOMs. They also state that the experiments described suggest that it may be possible to elicit human CTL by using ISCOMs containing HIV proteins, and that ISCOM-based vaccines may achieve the long sought goal of induction of both CTL and antibodies by a purified protein.
Byars and Allison, 5 Vaccines 223, 1987 describe use of SAF-1 which includes TWEEN 80, PLURONIC L121, and squalene or Squalane, with or without muramyl dipeptide, and suggest that their data indicate that the formulation with muramyl dipeptide will be useful for human and veterinary vaccines. Booster shots of the adjuvant were provided without the muramyl dipeptide. The muramyl dipeptide is said to increase antibody production significantly over use of the adjuvant without muramyl dipeptide. Cell mediated immunity was measured as delayed type hypersensitivity by skin tests to determine T-helper cell induction. Such hypersensitivity was stronger and more sustained when muramyl dipeptide was provided in the adjuvant. Similar adjuvants are described by Allison et al., U.S. Pat. No. 4,770,874 (where it is stated that the combination of muramyl dipeptide and pluronic polyol is essential to elicit a powerful cell mediated and humoral response against egg albumin); Allison et al., U.S. Pat. No. 4,772,466; Murphy-Corb et al., 246 Science 1293, 1989 (where it is stated that the use of combined adjuvants with muramyl dipeptide might enhance induction of both humoral and cellular arms of the immune response); Allison and Byars, 87 Vaccines 56, 1987 (where it is stated that cell mediated immunity is elicited by SAF (with muramyl dipeptide) as shown by delayed type hypersensitivity, by proliferative responses of T-cells to antigen, by production of Interleukin-2, and by specific genetically restricted lysis of target cells bearing the immunizing antigen); Allison and Byars, Immunopharmacology of Infectious Diseases: Vaccine Adjuvants and Modulators of Non-Specific Resistance 191-201, 1987; Morgan et al., 29 J. Medical Virology 74, 1989; Kenney et al., 121 J. Immunological Methods 157, 1989; Allison and Byars, 95 J. Immunological Methods 157, 1986 (where aluminum salts and mineral oil emulsions were shown to increase antibody formation, but not cell mediated immunity; and muramyl dipeptide formulations were shown to elicit cell mediated immunity); Byars et al., 8 Vaccine 49, 1990 (not admitted to be prior art to the present application, where it is stated that their adjuvant formulation markedly increases humoral responses, and to a lesser degree enhances cell mediated reactions to influenzae haemagglutinin antigen); Allison and Byars, 28 Molecular Immunology 279, 1991 (not admitted to be prior art to the present application; which states that the function of the muramyl dipeptide is to induce expression of cytokines and increase expression of major histocompatibility (MHC) genes; and that better antibody and cellular responses were obtained than with other adjuvants, and that it is hoped to ascertain whether similar strategies are efficacious in humans); Allison and Byars, Technology Advances in Vaccine Development 401, 1988 (which describes cell mediated immunity using SAF); Epstein et al., 4 Advance Drug Delivery Reviews 223, 1990 (which provides an overview of various adjuvants used in preparation of vaccines); Allison and Byars, 95 J. Immunological Methods 157, 1986 (which states that the addition of the muramyl dipeptide to the adjuvant markedly augments cell mediated responses to a variety of antigens, including monoclonal immunoglobulins and virus antigens); and Morgan et al., 29 J. Medical Virology 74, 1989 (which describes use of SAF-1 for preparation of a vaccine for Epstein-Barr virus).
Kwak et al., Idiotype Networks in Biology and Medicine, Elsevier Science Publishers, p. 163, 1990 (not admitted to be prior art to the present application) describe use of SAF without muramyl dipeptide as an adjuvant for a B-cell lymphoma idiotype in a human.
Specifically, an emulsion of Pluronic L121, Squalane, and 0.4% TWEEN-80 in phosphate buffered saline was administered with the idiotype. They state that "[a]ddition of an adjuvant should further augment . . . humoral responses, and may facilitate induction of cellular responses as well.
Other immunological preparations include liposomes (Allison et al., U.S. Pat. Nos. 4,053,585, and 4,117,113); cyclic peptides (Dreesman et al., U.S. Pat. No. 4,778,784); Freunds Complete Adjuvant (Asherson et al., 22 Immunology 465, 1972; Berman et al., 2 International J. Cancer 539, 1967; Allison, 18 Immunopotentiation 73, 1973; and Allison, Non-Specific Factors Influencing Host Resistance 247, 1973); ISCOMs (Letvin et al., 87 Vaccines 209, 1987); adjuvants containing non-ionic block polymer agents formed with mineral oil, a surface active agent and TWEEN 80 (Hunter and Bennett, 133 J. Immunology 3167, 1984; and Hunter et al., 127 J. Immunology 1244, 1981); adjuvants composed of mineral oil and emulsifying agent with or without killed mycobacteria (Sanchez-Pescador et al., 141 J. Immunology 1720, 1988); and other adjuvants such as a lipophilic derivative of muramyl tripeptide, and a muramyl dipeptide covalently conjugated to recombinant protein (id.).